Electronic structure and optical properties of bare and Li, Na, K and Ca coated C 60 molecule

Abstract

We study the electronic structure, geometric and low-energy optical properties of C 60 and metal-coated M 32C 60, where M = Li, Na, K or Ca. The one-electron Kohn–Sham orbitals are used together with the RPA matrix to calculate the screened oscillator-strength distribution. The deep-lying levels in M 32C 60 have C 60 character while those close to and above the Fermi energy have the character of the metallic M 32 layer. Isolated alkali M 32 shells are characterized by a double-peak structure in the range 1–3 eV, well below the π plasmon of C 60 at about 6 eV. In M 32C 60 the M 32 shell is coupled to C 60, but the characteristic double-peak can still be identified.